Warren County Mosquito Commission predicts busy summer

Wearing hip waders and carrying a 6-foot pole topped with a white cup, Stephanie Oliphant sinks into a few inches of standing water behind a baseball field at the White Township Recreation Area off Route 519.

Each cup of water the wetlands specialist with the Warren County Mosquito Commission scoops up reveals at least a half dozen squirming mosquito and pupae.

"They're ready to go," Oliphant said.

The wet spring has left the commission busy looking for mosquito eggs, and commission Superintendent Jennifer Gruener predicts a busy summer with the discovery of the aggressive Asian tiger mosquito in a new area of the county.

This has been a good spring for mosquitoes known as floodwater mosquitoes, which lay their eggs in areas that frequently see standing water, Gruener said. Rain will flood low-lying areas, cover eggs with the water they need to hatch and rain again a week later, submerging more eggs, she said.

Temperatures have generally been cool enough to give the commission a little time to catch up with control efforts, Gruener said. But despite the cooler temperatures the mosquito pupae found in White Township between the ball field and an abandoned rail line were a day from adulthood, five days after it rained.

"After a good rainfall, we're in a race against time," Gruener said.

Fishing for mosquitoes

The commission divides the county into four regions, each one with an established route identifying areas that are monitored and treated for mosquito activity. Gruener said the commission monitors more than 1,000 sites across Warren County -- fallow farm fields, vernal pools, ditches, swamps -- not including storm drains.

Control efforts center primarily on the larval stage because that's where you'll get the most bang for your buck, Gruener said.

"That's the stage we focus on for control because we know where they are," she said.

Some breeds -- there are 63 in New Jersey and 44 in Warren County -- prefer clean water, while others prefer the dirty, green water found at the bottom of abandoned swimming pools, Gruener said. The common denominator is still water, and the commission has mapped the sources.

Mosquitoes need still water because the pupae hang below the water with a siphon sticking above the surface. Aerators that churn the water's surface prevent them from maturing to adults because the mosquitoes essentially drown.

Along with an insecticide that affects only mosquitoes, black flies and midges, the commission deploys fish that eat as many mosquito larvae as they can find. The mosquito fish and fathead minnows, raised for the entire state at the Pequest Trout Hatchery in Mansfield Township, are a natural control measure for places like retention ponds and sections of the Morris Canal.

Gruener toured the county two summers ago for two weeks, looking for foreclosed properties. The commission dumped the fish into abandoned pools, ornamental ponds and even hot tubs, Gruener said. The commission makes the fish available to residents.

View full sizeThe aggressive Asian tiger mosquito, first spotted in Phillipsburg in 2012, has been found in Mansfield Township.Photo courtesy Greater Los Angeles County Vector Control District

Asian tiger spreads

The Asian tiger mosquito, meanwhile, appeared two years ago in Phillipsburg and in Alpha and last summer in Lopatcong, Pohatong and Greenwich townships, according to Gruener. They turned up about two weeks ago in a tire in Mansfield Township, she said, predicting that it's only a matter of time before they invade Hackettstown and Washington.

"The fact we found it so early and in a new area, I think it's really going to be a problem this year," Gruener said.

The aggressive mosquito, which is quickly becoming public enemy No. 1, bites during the day, lays eggs in artificial containers and needs little water to reproduce, Gruener said. Staff found an Asian tiger laying eggs in the ridges of a corrugated plastic pipe attached to a home's downspout, she said.

While the commission's efforts focus on preventing adult mosquitoes from even taking flight, staff monitors, traps and tests the adults for West Nile virus and the Chikungunya and Dengue viruses, which are carried by the Asian tiger.

Education is an equally important part of the commission's work, according to Sara May, the commission's mosquito identification specialist. Mosquitoes -- many of which have beautiful markings -- are critical for pollination and not all varieties bite humans, she said.

Homeowners are an important component in fighting the mosquito population, May said. Something as benign as a portable basketball pole can be a prime breeding ground, she said.

Water inside the base of a pole often overlooked by homeowners is warm and protected from predators, and it evaporates slowly, May said. The same can be said for an abandoned tire filled with water that can produce upwards of 50,000 mosquitoes a season, according to Gruener.

All it takes is a plastic bag or a discarded soda can and some rain: instant mosquito breeding ground.

"And that's where we need residents' help," Gruener said. "We can't to into everyone's backyard, we can't go door-to-door to clean up every backyard."